1. Technical Field
This invention relates to an x-ray fluorescence (XRF) analyzer and calibration methods of the x-ray fluorescence analyzer.
2. Field of the Invention
XRF is widely used to analyze a sample mass collected on a filter. An XRF analysis system includes three major components: an x-ray source, a sample and an x-ray detector. High energy x-rays are emitted from the x-ray source onto the sample to be analyzed. When the high energy x-rays hit the sample, new x-rays of differing energies are produced that are detected by the detector. The new x-ray energies are unique for each element in the sample. This process provides a spectrum, or chemical fingerprint, of the sample. The spectrum for each sample is analyzed to determine the components of the sample and the concentrations of those components.
XRF is a non-destructive analysis technique. Therefore, a sample analyzed by XRF is still available for reanalysis by XRF or another method. The technique can measure small concentrations in a relatively short analysis time for a wide range of elements. The accuracy of the XRF technique is limited to a specific dynamic range between the detection limits on the low end and saturation of the sample filter by particulate matter on the high end.
These sample measurements can provide plant operators with valuable information on plant efficiency, compliance efforts, and relationships between feedstock and emissions. On the other hand, inaccurate measurements could result in unnecessary regulatory restrictions, damage to health and the environment, and inappropriate plant operations.
In certain instances, it would be advantageous to use XRF to monitor the emissions of certain elements and compounds. The ability to use a continuous monitoring device based on X-ray fluorescence over long periods of time with confidence depends on the instrument's ability to provide automated quality assurance (QA) data proving that the instrument is working properly and that the results can be relied on at least to the accuracy and precision justified by the QA data. This is particularly important for continuous metals monitors that use filter tape to separate aerosol species from a gas stream and analyze the resulting deposits for metal content with X-ray fluorescence methods.
A problem with the prior art is that frequent calibration and quality assurance testing of the XRF analyzer is necessary if one wishes to rely on the results for proof of compliance with regulatory standards. Manual calibration and quality assurance take a lot of time and require the machine to be off-line.